Valve block

ABSTRACT

A valve block particularly for a medical or surgical ventilating machine allows easy cleaning and sterilization. The valve block has several nonreturn valves whose valve members are coplanar. These valves separate chambers in the block arranged to overlap each other in a chosen configuration to facilitate a desired pattern of interconnection.

United States Patent [72] Inventors Roger E. W. Manley;

- Charles J. A. Wellington, both 01 Chesham,

Buckinghamshire, England 838,738 July 3, 1969 Oct. 5, 1 971 Blease Medical Equipment Limited Deansway, Chesham, Buckinghamshire, England July 5, 1968 Great Britain 32258/68 Appl. No. Filed Patented Assignee Priority VALVE BLOCK 3 Claims, 8 Drawing Figs.

US. Cl

137/512, 137/454.5 Int. Cl F16k 15/14 Field of Search 137/512,

References Cited UNITED STATES PATENTS 4/1913 Butler 137/512X 6/1920 Rodriguez. 137/512 6/1927 Halleck 137/512 X 1/1953 Watson etal. l37/512X 12/1965 Elliott 137/512 FOREIGN PATENTS 2/1960 France 137/512 Primary ExaminerRobert G. Nilson Att0rneyF1eit, Gipple & Jacobson ABSTRACT: A valve block particularly for a medical or surgical ventilating machine allows easy cleaning and sterilization. The valve block has several nonreturn valves whose valve members are coplanar. These valves separate chambers in the block arranged to overlap each other in a chosen configuration to facilitate a desired pattern of interconnectionv BEST AVAILABLE COPY PATENTED 0m 5 IBYI sum 1 OF 5 I'PAIENIm-um 5l97| SHEET 2 0F 5 BET AVAILABLE COPY PATENTEDIJET 5|97| 3.610272 SHEET 3 [IF 5 Fla. 4

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sum 5 OF 5 INVENTORS Roger EW Manley Char/es JA. Wallingfon BY F leif G/pp/e 8Jacobs0n ATTORNEY 7 VALVE BLOCK 1 This invention relates to a valve block particularly but not necessarily exclusively for a ventilating machine for medical or surgical use.

Ventilating machines are currently used in hospital environ- 'ments where it is very important that they should be sterile, otherwise cross infection with serious consequences is probable. In current ventilating machines several nonretum valves are necessary and their assembly and disassembly for cleaning and sterilization, coupled with their relative inaccessibility in known machines present problems. In particular it is not possible in most current practical machines for effective disassembly, cleaning and assembly to be done by persons such as nurses who are relatively unversed in the technical complexities of the machines. It is an aim of the present invention to mitigate this disadvantage.

According to the invention in its broadest aspect, we provide a valve block containing a plurality of nonretum valves, characterized in that the valve members of at least two of the valves are coplanar.

In one embodiment of the invention the valve block is characterized in that it comprises two separable portions each having a plane surface adapted to engage the plane surface of the other in a fluidtight manner, each of the portions having registering recesses to accommodate respective nonretum valves and also having passages connecting the said recesses with each other or with the exterior of the respective portion as may be required. In such an arrangement some of the recesses of each block contain valve seats each cooperating with the valve member of one of the nonretum valves.

In a second embodiment of the invention, the valve block is formed at least partly as a body of revolution and defines the axially spaced groups of chambers, at least one chamber of the first group overlapping more than one chamber of the second group, with the two groups being separated by a planar web having a plurality of apertures at least two of which accommodate respective nonretum valves controlling flow between a chamber of the first group and a chamber of the second group. Preferably the aforesaid valve block is formed by a body of revolution having a web extending generally laterally of the axis and separating a first group of chambers in the block partly defined by partitions from a second group of chambers inthe block also partly defined by partitions, at least some of the chambers of the second group having shapes not identical with those of the first group.

Advantageously the valve block is bounded by a substantially cylindrical external wall and has a central bore. The web desirably has a plurality of apertures therein which can house valves connecting the various chambers in a way appropriate to the desired circuit which is to be accommodated in the valve block.

The partitions partly defining one or both groups of chambers are preferably substantially radial.

The block may have opposed plane boundary surfaces norinal to its axis, each of these being capable of cooperating with a sealing gasket clamped thereon by a cover plate. A threaded rod may be passed through the central bore, carrying a nut by which the cover plate can be clamped, so that disassembly for cleaning and sterilization purposes can be accomplished merely by unscrewing the nut on the rod and removing the cover plate and the gasket. This feature is of importance in practical use in that simplicity in disassembly for cleaning assists hardpressed hospital staff such as nurses to maintain correct cleaning procedure.

The valve block may be made as a single casting of castable 'metal. The end faces of the block may conveniently be turned flat and bores made through the lateral web to accommodate valves connecting the chambers. Alternatively it may be made from mouldable synthetic plastics material, for example by a pair of appropriately shaped tools moved axially towards each other.

With a valve block as disclosed in either of the embodiments herein, the nonretum valves referred to can be mounted for easy cleaning and sterilization. Furthermore the necessary disassembly and assembly is easily effected. The invention will now be particularly described in the following description of illustrative embodiments, given by way of example and with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 shows part of the machine and corresponds to FIG. 2 but shows the tap 354 in its manual operation position; in this case the bag 357 is squeezed by hand to force air into the patients lungs. This FIG. includes the optional respirometer 96, 97 omitted in FIG. 2.

FIG. 2 shows part of the machine and illustrates the opencircuit system, that is to say air after passing to the patient is discharged to the atmosphere, the tap 354 being shown in its automatic operation position.

FIG. 3 is a diagrammatic section through a first embodiment of valve block according to the invention.

FIG. 4 is a diagrammatic plan view of the two portions of the valve block shown in FIG. 3 with the upper" portion folded open, i.e. inverted and placed below the lower" portion.

FIG. 5 is a detail view in vertical section showing one possible construction of nonretum valve and its location at the junction of a recess in the upper block with one in the lower block.

FIG. 6 is a plan view (looking downwardly) of one side (e.g., the top) of a second embodiment of valve block according to the invention.

FIG. 7 is an underneath plan view (looking upwardly) of the other side (e.g. the bottom) of the valve block shown in FIG. 6.

FIG. 8 is a diagrammatic section of the valve block according to FIGS. 6 and 7.

Two forms of machine for embodying a valve block according to the invention are illustrated in FIGS. 1 and 2 but the basic cycling box'mechanism of the machine and the trigger mechanism thereof are common to both the embodiments. In addition the nonretum valves 48, 49, 51, 52 and 53 are common to all the embodiments, and the present invention is directed to a compact and easily disassembled valve block containing these valves.

The cycling mechanism which includes parts 333, 334, 335, 339, 340, 341, 342, 343, 344, 345, 346, 347 and valve 48, is housed in a large, sealed, cast aluminum box (FIG. 1) with 'the trigger mechanism (321,324) mounted above it. These two mechanisms together provide all the controls for pressure, phasing and frequency for all the patient circuits. They will only be briefly described since they form no part of the novelty of the invention.

CYCLING BOX MECHANISM The box consists of two chambers 317 and 317A separated by a diaphragm 334. Air from a pump (not shown) enters one chamber continuously. When valve 47 is closed the air travels up to the bellows chamber 317, compresses the bellows 313, and produces inflation of the patients lungs, the face mask being connected to pipe 262. When the pressure in the chamber 317 produces a force on the diaphragm equal to the spring 335, the diaphragm moves to the right causing the pawl 339 to disengage from the wheel 340. When this happens valve 47 opens by the force of the spring. This causes the pressure in the chamber to fall to atmospheric and inflation ends. The valve 49 then opens and expiration takes place under the influence of the venturi tube 342 and 343. The spring 335 now forces the diaphragm back with air entering via needle valve 338 until the pawl 341 disengages from the wheel. Valve 47 not shuts starting theinfiation cycle.

THE CONTROLS OF THE CYCLING BOX MECHANISM a. Rate of Inflation The needle valve 346 regulates the inspiratory flow and is continuously variable. The mechanism is so designed that to initiate inflation a high peak flow (140 liters/minute is available. The-flow is reduced as inflation proceeds and it is the reduction in flow that is set with this control.

The needle valve 346 allows air to pass from the chamber 317 to atmosphere. The flow through the needle valve 346 is proportional to the pressure in the chamber and produces a decreasing flow as the inflation pressure rises. It is this control that produces an inspiratory plateau if this is required, and determines the duration of the inspiratory phase.

b. Expiratory Pause Control.

When the diaphragm 334 moves to the right, the air in the chamber 317A is expelled through the one-way valve 333. During the expiratory phase the diaphragm moves to the left and the time taken is determined by the needle valve 338. This control determines the duration of the expiratory phase.

c. lnflation Pressure Control.

The inflation pressure control 335 sets the pressure at which diaphragm 334 moves. 1f the ventilator is being used as a presconsisting of venturis 342 and 343 and a tap 344 to proportion the flow between them. This will produce any expiratory pressure from to -l0 cm. water gauge.

The Controls on the Trigger Mechanism a. Trigger ON/OFF Tap.

The tap 320 is used to turn the patient trigger facility ON for assisted ventilation. 1n the OFF position the ventilator is independent of any efl'ort by the patient. When the tap 320 is in the ON position the frequency of ventilation is entirely controlled by the patients inspiratory efforts if the expiratory pause control" is set to allow a long expiratory phase. If the ventilator is required to be used as an assistor/controller, the expiratory pause control" (above) is adjusted to give the required basic frequency. Any inspiratory effort made by the patient during the expiratory pause will increase this frequency. If no effort is made the ventilator runs at the basic frequency.

The patient trigger facility is operated by the inspiratory effort of the patient lifting diaphragm 323. This opens valve 324 and causes air to enter the chamber in the box mechanism. Diaphragm 334 moves to the left and closes valve 47.

b. Trigger Negative Pressure Control.

The negative pressure control 321 regulates the inspiratory eflort pressure from the patient needed to initiate inflation. It can be set from 1 to 6 cm. water gauge. It is used to encourage a recovering patient to make greater inspiratory effort in preparation for spontaneous ventilation. With this control the trigger may be used in conjunction with a negative expiratory phase. It is the balance between the spring associated with the diaphragm 323 and the force on the diaphragm that regulates the trigger sensitivity. Once set this is locked by a ring 322.

The Open Circuit System The patient open circuit is illustrated in FIGS. 1 and 2 and consists of two basic circuits; one for automatic ventilation, and one for manual ventilation. Selection is controlled by tap 354 A, B, C and D.

Automatic Ventilation (SEE FIG. 1)

The inflating bellows 313 is housed in an antistatic glass jar 313A on top of the machine. The jar is connected to the cycling box mechanism and shares the pressure changes that occur there. Inside the bellows there is a rod and stop 314 which limits the upward movement of the bellows when pressure is exerted on the outside of the bellows. The rod can be raised or lowered by screw 311 and locked by ring 312. This device limits the tidal volume and enables the ventilator to be used as a volume cycled device. The arrow 316 indicates on the calibrated scale 318 the tidal volume setting from 100-l 200 cc. Locking screw 319 enables the scale to be raised to compensate for compliance in the circuit.

Ventilation on Open Circuit using Gas or Oxygen or Air Each time the bellows 313 descends at the end of an inflation gas is drawn through valve 52. As long as the fresh gas supplied at inlet 363 equals the minute volume set on the ventilator i.e., the tidal volume multiplied by the frequency, then the bellows will fill entirely from the bag 360. The valve 51 will stay closed and pure gas will be supplied to the patient. if the volume of gas supplied at inlet 363 is in excess of that required then spill valve 361 will open but if the volume is less than that required by the bellows then the bag 360 will empty and air will be drawn in through filter 59 and valve 51. This enables gas/air mixtures to be used and is especially useful for air/oxygen mixtures. The required flow of oxygen is set and the ventilator automatically mixes this with air to the required minute volume set on the ventilator. When no fresh gas is added to the ventilator delivers pure air. When the bellows rises, gas and/or air flows through valve 53 to the patient via tube 364 and tube 262 of the Y piece. During expiration gas travels via tube 358 to valve 49 and to the venturi system 342. 343. The inflation pressure reached is shown on gauge 310.

Operation of Open Circuit System Pressure Cycled.

The rod and stop 314 is screwed right up to prevent tidal volume limiting. The frequency, inflation pressure and expiratory pressure are set on the cycling box mechanism. The fresh gas is set to the required level.

Volume Cycled. The outlet 262 is closed and the reserve pressure is set on control 335. This gives the maximum pressure then can be reached during volume cycling and acts as a safety device. The tidal volume, frequency and expiratory pressure are then set.

Manual Ventilation (see FIG. 2) The tap 354 A-D is turned through degrees to its manual ventilation position. This has four effects:

1. connects the cycling box mechanism to atmosphere and stops the automatic cycling, (A)

2. diverts the fresh gas to bag 357 via tube 356, (B)

3. connects bag 357 to patient at 262 via tubes 356 and 358, (C), and

4. connects expiratory valve 365 to patient via tube 364, (D). The outlet 398 is an outlet from the cycling box mechanism (317 etc.) which is used during manual ventilatlon.

VALVE BLOCK CONSTRUCTION As will be appreciated, the valves 48, 49, 51-53 will require cleaning and sterilization after each use of the machine and to facilitate this a single valve block containing then and consisting of two separable portions is provided. The valve block 100 (FIGS. 3 and 4) is not shown 'as such in FIGS. 1 and 2 and has an upper portion 102 and a lower portion 104 and the latter has a plane surface with six recesses 105-110 therein. Four of these recesses (105,106, 109 and 110) contain a valve seat 112 and a valve diaphragm 114 resting on the seat, as illustrated in detail in FIG. 5. The valve seat is a screw or press fit in its associated recess 116 and has apertures so that gas or air can pass from within the recess 116 to the underside of the diaphragm 114. The diaphragm is a flexible rubber or plastics or like material and lifts off the circumferential part 118 of the seat 112 under the gas or air pressure. Under back flow conditions the valve diaphragm 114 seats firmly on the seat 112. Thus each of the valves in the recess 105, 106 and 109 functions as a simple nonreturn valve. The recess 110 is much smaller than the other three and its valve 48 is correspondingly smaller but in other respects it is similar. The valves in the recesses 105, 106, 109 and 110 are respectively valves 51, 52, 49 and 48 of FIGS. 1 and 2. The parts of th valves that stand proud of the plane surface of the portion 114 are accommodated in registering recesses in the valve block portion 102. The recess 108 serves to accommodate those parts of the valve to be described in recess 128 that stand proud of the block portion 102.

The upper portion 102 of the valve block has a plane sur face to mate with the plane surface of portion 104 and has six recesses 125-130 which register with the aforesaid recesses 105-1 respectively.

The central recess 107 cooperates with a corresponding central recess 127 in block portion 102 and communicates directly with the interior 313 of the bellows. A guide 132 is provided for the tidal-volume adjusting screw 311 which, as described, acts by limiting the extent to which the bellow can contract. The upper portion 102 of the block has a bore 140 connecting recesses 126 and 127, and a bore 142 connecting recesses 127 and 128. Further bores 144 and 146 respectively connect recesses 125 and 129 to portions in the valve block.

The lower portion 104 of the block 100 has a bore 150 that enters from one side, extends under the base of and past the recess 107, and joins a blind slot 152. The blind slot 152 communicates with the recesses 106 and 110 housing valves 52 and 48. in use, fresh gas is fed to the bore 150 and this passes via the recess 106, valve 52, recess 126, bore 140 and recess 127 to the bellows 313. Also if supplied at too great a pressure it can lift the safety valve 48 and pass via recess 130 and a hole 156 (FIGS. 3 and 4) to atmosphere. The recesses 108 and 109 are respectively connected to the exterior of the block portion 104 by bores 158 and 160. These bores are connected to the patients face mask. When the patient exhales or is forced to do so the gas passes along the bore 158 but is prevented from going further by valve 53. The gas exhaled does however pass valve 49, through the bore 146, and to the tube containing venturis 342 and 343 (FIG. 1 and 2). Thus lifting (i.e. opening) of the valve 49 allows air or gas to be drawn from the pa tient via bore 160, recess 109, valve 49, recess 129, and bore 146. Valve 49 thus acts as a nonreturn valve from the patient circuit.

The bore 158 is connected to the face mask for the patient and valve 53 acts as an air inlet nonreturn valve or as an inhaling valve as the case may be. If an open-circuit operation (FIG. 1 or 2) the bellows 313 are contracted to cause the patient to inhale, the air or gas therein is expelled via recesses 107, 127, bore 142, past valve 53 which is thereby opened against its biassing spring, and recess 108, and then passes to the patient via the bore 158. If on the other hand the patient exhales, the air enters the bore 158 and recess 108 but cannot pass valve 53 because of its nonreturn characteristic and the fact that it is kept closed by its biassing spring 53a.

The recess 105 in block portion 104 is connected via a bore 162 to an air intake filter 59 (FIGS. l-4).

It will be seen that this arrangement is a convenient and accessible one and the general principle of splitting a valve block at a plane can be employed in any type of apparatus where numerous valves requiring maintenance, adjustment, cleaning or sterilization are included. While a specific circuit arrangement has been described it will be realized that the invention is not limited thereto.

A second embodiment of valve block according to the invention will now be described.

The valve block illustrated in FIGS. 6 through 8 has a central axial bore 272 and first and second groups 10 and 12 of chambers, and is of an approximately cylindrical shape. It has opposed faces that are parallel to each other. The block illustrated is intended for use in a ventilating machine having a circuit as described and illustrated in FIGS. 1 and 2 herein but it will be appreciated that the principles underlying this embodiment of the invention can be applied in any fluid circuit, whether it be hydraulic or pneumatic, so long as it includes valves to which access is desirable for inspection, maintenance, cleaning, adjustment or other purpose. For illustration, the valve block illustrated in FIGS. 6 through 8 will be described with reference to the aforesaid ventilating machine circuit.

The upper surface of the valve block has recesses constituting a first group of chambers 14, 16, 18 and 20 defined by an internal part cylindrical wall 26, an external cylindrical wall 28, partitions 30, 32, partial partition 36, and a thickened partition 38. The lower surface has recesses constituting a second group of chambers 44, 46, 248 and 50 defined by an internal cylindrical wall 56, and external cylindrical wall 58, and partitions 60, 62, 64 and 66. In FIG. 6 the partitions 62-66 of the second group are indicated in dotted lines, and likewise in FIG. 7 the partitions 32, 36, and 38 are similarly indicated by dotted lines. The walls 26, 28, the partitions 30-38, the walls 56, 58, and the partitions 60-66 are all integral with the block. The block may thus be fabricated by casting or moulding, either in metal or in a suitable synthetic plastics material. It may for example be fabricated by opposed dies of suitable configuration being moved towards each other to form the first and second groups of chambers in opposite surfaces of the block.

The block while generally cylindrical in shape, has two projections 70 and 72 thereon. These are provided to facilitate the fitting of external connections supplying air or gas to the various chambers as will be described. The projection 70 is intended to accommodate a first bore 71 opening into the chamber 18 and a second bore 73 located below the first bore 71 and opening into chamber 248. The projection 72 is intended to accommodate in its upper half a third bore 75 opening into the chamber 20 and putting the said chamber into communication with the ambient atmosphere and in its lowerhalf three parallel bores 80, 82, 84 for making connections as will shortly be described. It will be seen that the first and second groups of chambers are separated by a web extending transversely of the axis of the valve block and that chambers 46 and 248 of the second group have shapes differing from those of chambers 16 and 18 of the first group. This feature allows a particular pattern of interconnection to be inexpensively and efficiently achieved without additional piping, glands and couplings and in accordance with the requirements of a particular fluid circuit.

As seen in FIG. 8, gaskets 399 and 400 are positioned between respective cover plates and serve to seal off the respective chambers.

The application and use of a valve block according to the invention in a ventilating machine circuit will now be described. The circuit involved in this particular application is that illustrated in FIG. 1 and the valve block illustrated herein is intended to include valves 48, 49, 51, 52 and 53 of FIG. 1. Valve 53 is the inhalation valve and valve 49 is the exhalation valve, these being connected to the patient or user of the ventilation machine via a pair of flexible tubes, a pipe 262, and a face mask as is conventional in the art.

For ease of understanding, these five nonreturn valves are indicated by circles in FIGS. 6 through 8 and bear the same references 48, 49, 51-53.

The bellows 313 (not shown in FIGS. 6 through 8) is mounted in association with the valve block of FIGS. 6 through 8 so that its interior is in direct communication with the central axial bore 272 defined by wall 26. Because of the cutaway portion of the inner circumferential partition 26 it is thus in direct communication with the chamber 14. The valve 53 is located in the lateral web defining the two groups of chambers and is spring biassed to open downwardly when a certain pressure, for example greater than 25 cms. water gauge, exists in chamber 14. Such a pressure will of course be caused by contraction of the bellows 313.

When the valve 53 opens, gas from the machine passes through the lateral web into the chamber 44 and thenceto the face mask via bore 80. When the patient exhales, the exhaled gas comes along bore 84 and enters chamber 50, passes through nonreturn (exhalation) valve 49, and into chamber 20. Thence it passes via bore 75 to atmosphere.

The fresh anesthetic or analgesic gas is supplied along bore 82 (FIG. 7) into a bore 86 opening into the chamber 14. The end of the bore 86 is plugged with a cap 87 to which a pipe connection 150 is joined. This pipe 150 conveys the fresh gas to a hollow cap 89 plugging a bore 88 in the lateral web extending through to chamber 46. The pipe 150 of FIG. 6 corresponds to the bore 150 of the FIG. 4 embodiment of valve block. The hollow cap 89 opens into chamber 46 (the mixing chamber).

Also supplied to the mixing chamber 46 is air via bore 73, air chamber 248, nonretum valve 51, chamber 18, and a bore 90 through the lateral web in the zone thereof where chambers l8 and 46 overlap. Connected to the chamber 18 by the bore 71 is a flexible bag constituting a reservoir of anesthetic gas. This allows short term manual operation if the supply of anesthetic gas to bore 82 should be momentarily halted, for example when changing cylinders.

In the thickened partition dividing chambers 16 and 18 is located a bore 270 containing the nonretum safety valve or spill valve 48. This bore opens into a mixing chamber 46 and the valve 48 opens to relieve pressure when a given safety level is exceeded. The relieved gas passes to atmosphere out of the top of the valve block.

Thus far, connections to provide the desired mixture of air and anesthetic gas to the mixing chamber 46 have been described. The last nonretum valve is a nonretum valve 52 in the lateral web separating mixing chamber 46 and the chamber 16. The valve 52 is spring biassed to open upwardly, allowing mixed gas and air to pass from mixing chamber 46 to chamber 16 under the conditions shortly to be described. Because of the interruption in the partition 36, the chamber 16 is in communication with the chamber 14 and the latter is (as stated) in communication with the interior of the bellows via the central axial bore 272 in the valve block. When the bellows are expanded the reduced pressure so induced exists in chambers 14 and 16 and causes the nonretum valve 52 to open, allowing the bellows to be recharged with fresh gas-air mixture which upon the next contraction of the bellows will be supplied to the patient in the manner already described.

It will be seen that the aforesaid circuit corresponds to that illustrated in FIG. 1.

Advantages of the embodiments of valve block specifically disclosed herein are firstly that assembly and disassembly are easy, thus sterilization procedures are more likely to be carried out according to directions by hard-pressed hospital stafi; also the arrangement of the nonreturn valves in one plane makes access easy, and that (in the case of the FIGS. 6 through 8 embodiment) manufacture of the valve block especially by moulding or casting can be efficiently arranged, thus making possible a hitherto highly desirable but impossible practice, namely use of disposable" ventilation circuits. This last feature is of particular value in the case of a machine used for a patient having an infection that is highly resistant to antibiotics. Furthermore the design of the block of FIGS. 6 through 8 is such that it is easy to fabricate it in rigid antistatic material. A rigid structure is desirable because of the compliance (i.e. volume variation with pressure changes) of equipment which uses piping and separate valves. By the present design it is possible to reduce compliance of the ventilating machine to a minimum.

it will be appreciated that the invention is not limited to the specific arrangement described and illustrated herein. Modifications can be made without departing from the principle of a valve block constructed for a particular circuit by a suitably chosen arrangement of valves and overlapping chambers.

We claim:

1. A valve block comprising:

a. a body formed integrally from a single piece of material and having a longitudinal axis, the body being bounded in part by two parallel plane boundary surfaces transverse to the axis,

b. a web forming part of the body and disposed transverse to the axis, c. partitions forming part of the body and in part defining recesses and being disposed to form at least two groups of chambers of which at least one chamber of the first group overlaps more than one chamber of the second group viewed in an axial direction, the two groups being separated by the web,

d. passages in the body each communicating with at least one of the chambers,

e. a plurality of nonretum valves in the web providing for fluid communication between selected chambers of the two groups in accordance with a desired scheme of interconnection,

f. the body being formed with the chambers of the two groups spaced around a central bore extending complete ly through the body, the bore being defined by parts of the chamber walls,

. a sealing gasket and cover plate associated with each said plane boundary surface, and

h. a threaded member passing through the said central bore and carrying means for clamping the said cover plates and gaskets to their confronting plane boundary surfaces, whereby disassembly of the valve block for access to and cleaning of the said chambers by unskilled personnel is facilitated.

2. A valve block according to claim 1 wherein the web is planar and normal to the axis.

3. A valve block according to claim I in which the valve members are constituted by circular discs seating on respective annular valve seats located on respective walls of the recesses. 

1. A valve block comprising: a. a body formed integrally from a single piece of material and having a longitudinal axis, the body being bounded in part by two parallel plane boundary surfaces transverse to the axis, b. a web forming part of the body and disposed transverse to the axis, c. partitions forming part of the body and in part defining recesses and being disposed to form at least two groups of chambers of which at least one chamber of the first group overlaps more than one chamber of the second group viewed in an axial direction, the two groups being separated by the web, d. passages in the body each communicating with at least one of the chambers, e. a plurality of nonreturn valves in the web providing for fluid communication between selected chambers of the two groups in accordance with a desired scheme of interconnection, f. the body being formed with the chambers of the two groups spaced around a central bore extending completely through the body, the bore being defined by parts of the chamber walls, g. a sealing gasket and cover plate associated with each said plane boundary surface, and h. a threaded member passing through the said central bore and carrying means for clamping the said cover plates and gaskets to their confronting plane boundary surfaces, whereby disassembly of the valve block for access to and cleaning of the said chambers by unskilled personnel is facilitated.
 2. A valve block according to claim 1 wherein the web is planar and normal to the axis.
 3. A valve block according to claim 1 in which the valve members are constituted by circular discs seating on respective annular valve seats located on respective walls of the recesses. 